I came across Chris_Pratley's WebLog the other day - it's a good read. Chris is Group Program Manager for Office Authoring tools, which includes OneNote. one of the guys who runs the OneNote product. His blog contains some great insights into the how and why's of OneNote.
OneNote is an incredibly cool tool - it reminds me a bit of some of the outlining tools I used in the mid-80s. I use OneNote today fairly heavily to organise my thoughts. I suspect that if I ever get a tablet, I'd use OneNote a lot more!